Fluid-engineering assemblies frequently contain non-return valves as components of the control systems of the assemblies. In many practical applications, controls using non-return valves with fixed opening pressures, are not trouble-free because of the variable configuration of the assemblies (with regard to pressure level, volume flow, site of installation, and the like). In such case, the non-return valve must be replaced with a valve set for the opening pressure adapted to the assembly when the assembly is placed in operation on site. This replacement entails burdensome and time-consuming conversion measures. In some instances, it must be executed repeatedly because the opening pressure required in individual cases cannot be accurately foreseen. A remedy can be in the form of a non-return valve that could be adjusted as a function of the opening pressure.
Currently available adjustable non-return valves cannot, however, meet the requirements to be set. Conventional valves with adjustable opening pressure are configured as pressure control valves. Aside from the fact that pressure control valves are not well suited for the purpose with respect to adjustment ranges, pressure stages, and temperature ranges, the chief problem encountered with pressure-control valves is that the flow of fluid is diverted at an angle of 90° downstream from the adjustment device. Fouling particles may then be deposited on the valve seat for fouling-laden fluids and may then cause the valve to fail.